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The agronomic advantage of the T1BL. 1RS translocation and the potential importance of chromosome 1BS to end‐use quality of bread wheat (Triticum aestivum L.) warrant a more precise definition of the relationship of T1BL‐1RS to bread wheat quality. This study was conducted to determine the effect of TIBL. 1RS from ‘Aurora’ on grain and flour quality in multiple near‐isoline pairs with varying genetic background, and to examine the genetic variation among random inbred lines selected only for 1B or T1BL 1RS. Two experiments were conducted, each with a different set of genetic materials derived from the same pair of crosses. In one experiment, 25 pairs of F5‐derived near‐isolines homozygous for either 1B or T1BL‐ 1RS were evaluated in at least two environments; in the second experiment, plants homozygous for either 1B or T1BL‐1RS were selected in the F2, and 40 inbred lines per chromosome type in each cross were evaluated in four environments. The near‐isolines showed high isogenecity for all traits based on comparison of duplicate lines within pairs. The translocated chromosome, on the average, increased grain protein concentration and decreased mixogram rating, mlxogram band width, and sedimentation volume in both crosses. Kernel hardness, flour yield, and mixing time either decreased or did not change in the TIBL 1RS isolines depending on the cross. Water absorption did not change. The T1BL‐1RS and 1B isolines showed similar mixograph properties in eight of the 25 pairs. Genetic variance of TIBL IRS random inbred lines was not reduced for those traits where deleterious effects were most notable, e.g., mixing tolerance and sedimentation volume. Hence, the detrimental effect of T1BL‐ 1RS on dough properties might be mitigated, relative to non‐TIBL 1RS genotypes with equivalent pedigree, by rigorous selection of background genotype. Special attention must be given to mixing tolerance and sedimentation.

Flag leaves of many diploid and tetraploid Tritlcum species are known to have higher photosynthesis rates than flag leaves of cultivated hexaploid wheat (Tritlcum aestivum L.). Yet these differences are reportedly absent or less pronounced on earlier developed leaves. Our objective was to study the relationship between photosynthesis, stomatal conductance, and water-use efficiency (WUE) in various Triticum acessions at the tillering stage. Net CO2 assimilation per leaf area (A) and associated gas exchange characteristics were measured on newly expanded leaves of 6-week-old growth chamber-grown plants of four wild diploids, six wild tetraploids, and two cultivated hexaploids. Significant variation in A was observed with values ranging from 31.1 ~mol CO2 m-2 s-I in the diploid T. speltoldes to 20.7 in one accession of T. dicoccoides; A for the two hexaploid wheats averaged 22.6. This A range for leaves of plants at tillering is similar to that reported by others measuring A of tlag leaves. Because higher A was associated with higher stomatai conductance (r = 0.86"*, significant at the 0.01 probability level), which led to higher transpiration, there was no significant correlation between A and WUE. There was no significant correlation between A and internal CO2 concentration (C~), so differences in A among accessions were not explained by differences in CO2 supply to the mesophyll. Two T. dicoccoides accessions found to differ in A and conductance at tillering also had different flag leaf A and conductance. Comparison of A vs. Ci response curves between these two accessions showed that the higher A was related to a higher capacity for mesophyll photosynthesis rather than stomatal conductance per se. The results show that the variation in A among accessions was to a significant extent attributable to nonstomatal factors and that differences in A among Triticum accessions are detectable at early vegetative growth stages.

Awned hard red winter wheat (HRWW, Triticutn aestivum L.) cultivars have prevailed in the Great Plains since the introduction of 'Turkey' wheat in the 1870s, but the role of awns in wheat productivity is unclear. Awns may serve a photosynthetic function during periods of drought stress, and may actually compensate for flag leaf photosynthesis reduced by drought stress. Our objectives were to determine the effect of genetic awn suppression on photosynthesis and instantaneons or season-long measurements of water-use efficiency (WUE), and to monitor associated changes in kernel characteristics. Plants of awned and awnletted near-isogenic lines of three contemporary HRWW cnitivars (TAM 107, Century, and Mustang) were grown controlled-environment chambers under well-watered and waterdeficit conditions. Photosynthetic rates of spikes and flag leaves were measured separately at two stages of kernel development. Whole-plant and grain WUE were measured based on actual water use. Under well-watered conditions, net photosynthetic rates of awnletted spikes were significantly lower than awned spikes for all cnitivars at 1~1 d after anthesis (DAA) and for two cultivars at 24 DAA. Under water-deficit conditions, rates were significantly lower for awnletted spikes of Mustang and TAM 107 at 14 DAA, while no differences were found at 24 DAA. No differences were found between isolines for flag leaf photosynthesis at either stage. Generally, differences in kernel characteristics were nonsignificant between awned and awnletted lines. Although some instantaneous photosynthetic measurements suggested higher WUE of awned spikes, this difference did not result in higher WIrE based on whole-plant biomass or grain weight for awned isolines.

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